This request is for funds to purchase a JEOL 1400 transmission electron microscope. This instrument will be housed within the Center for Biologic Imaging (CBI) at the University Of Pittsburgh School Of Medicine. The mandate of this core facility is to provide access to a full range of light and electron optical, image analysis, and morphometric methods to all research groups within the University Of Pittsburgh School Of Medicine. Electron microscopy is an essential service provided by the center, the current core use electron microscopes within the facility are a JEOL 1011 and 1210. The 1011 is operating at capacity. The 1210 is 18 years old and reaching the end of its useable life. In the last year we have had multiple significant failures, these related to camera problems, a variety of computer failures, general vacuum failures and other mechanical (lens) failures. In each case these failures tend toward catastrophic rather than trivial because quite simply the engineers do not know how to fix the problems and the parts needed are either very rare or cannot be found. These failures are difficult to deal with as the use of EM within the center has continued to grow such that we are no longer able to satisfy user needs without two fully functional microscopes. Therefore, the reasons for this application are to: 1: Provide critically needed instrument time; 2 Replace the 1210 instrument which is no longer serviceable as a core microscope. Since the CBI commenced operations over 20 years ago, it has become an integral part of the medical research community currently participating in research projects with more than 250 PHS funded groups within the medical area, as well as in PHS supported projects with investigators at institutions around the country. As the PHS funded user base continues to expand, a lack of quality EM time has become a major limiting factor in the utility of the center, this leads to considerable frustration amongst users.